Surfactant treatment of microballoons to improve water resistance



United States Patent SURFACTANT TREATIVIENT 0F MICROBALLOON TO IMPROVE WATER RESISTANCE I No Drawing. Application December 31, 1954" Serial No. 479,251"

9 Claims. (Cl. 21-605) The present invention relates to the inhibition of the evaporation of volatile non-aqueous liquid products by a floating layer comprising small, hollow, hole-free particleswhich have been treated with a water-insoluble, ionic, surface-active agent.

Copending application S. N. 389,472, filedOctober 30, 1953, discloses that the evaporation loss of volatile products can be effectively. decreased and inhibited by floating thereon a layer of individual, small, hollow, gas filled, hole-free particles of a material inert to the volatile product, which particles have an average diameter of less than 500 microns and a liquid displacement density of from 0.05 to 0.6.

These particles will spread out upon the surface of a volatile non-aqueous liquid to form a layer of uniform thickness. An inspection of this layer will showthat the particles are tightly packed together and this layer prevents evaporation of the liquid. It has been found, however, that exposureto moisture such as thatynormally found in the atmosphere will alter the characteristics of the layer. .The water-wetted particles will begin to agglomerate whereby the layer will assume an uneven appearance. After further exposure to moisture or rain, agglomeration will continue until openings in the layer develop. Agglomeration is accompanied by an increase in the rate of evaporation, thereby defeating the purpose for using the particles. water in the layer may become so large that, where the volatile liquid covered has a density lower than water, the water, carrying entrained particles, will sink.

It has been observed that those particles which have Ultimately the proportion of been exposed to rain or humid atmospheric conditions do not pack together as uniformly and tightly as in the absence of moisture, nor are they as easily wetted by the volatile non-aqueous liquids. It has also been observed that the ability of a layer of these particles to inhibit evaporation is directly related to the ability of the particles to be wetted preferentially by the volatile nonaqueous liquids as opposed to being wetted bywater. In other words, the sensitivity of these particles to moisture impairs their ability to inhibit the evaporation of volatile liquids.

Accordingly, it is an object of the present invention to provide small, hollow, hole-free particles having a lower sensitivity to water.

Another object is to provide methods for treating hollow, hole-free particles whereby said particles are rendered less sensitive to water.

Still another object is to reduce the rate of evaporation of volatile non-aqueous liquids by means of placing thereover a layer of small, hollow, hole-free particles of low water sensitivity.

These and other objects, as well as the utility and advantages of the invention, will become apparent from the following detailed description.

it has now been found that small, hollow, hole-free 2,822,238 Patented Feb. 4, 1958 particles of the-type mentioned :above can be rendered less sensitive to water by treating them with an appreciable amount up to forty percent, based on the weight of said particles,- of an ionic, water-insoluble, surfaceactive agent. ..Not only. are these treated particles less sensitive to water but, surprisingly, their use as a floating layer over volatilevnon-aqueous liquids will substantially reduce the rate of evaporation. as compared with av layer of untreated particles.

The use of hollow particles 'with a very small amount of surface-active agent will give some improvement over untreated particle's: Substantial improvements have been observed withfabout 0.1% 'agent which is approximately an amount suflicient to provide a monomoleculancoating over the'ho llow. particles. Surprisingly, continued improvements are possible when. the amount is increased to ten. percent and even to forty percent. Accordingly, the upper limit willbeinfiuenced more by economical than by technical considerations. V

Thefiionic surface-active agent; of the present invention may be anionic'or cationic. All'must be characterized by a molecular-structure so as to be chemically inert to and insoluble in water; Water insolubility is recognized as a relative term. Thus, in this invention, water-insolublef1 surface-active agents. also include those agents which :are only slightly soluble in water. Operable agents: williresist the leaching eifectof water, such as by rain falling.ontoraifloating layerof treated. particles, thereby giving a floating layer which. will not:readily deteriorate in the presence of moisture. Generally, the surface-active agents of the present invention are oil soluble, but the latter is not a criterion of operativeness. Operable anionic-.surface-active agents include waterins'oluble carboxy acids, sulfuric esters, alkane sulfonates and alkyl aromatic, sulfonates. .Cationic surface agents include amino and quaternary ammonium compounds. These types of surface-active agents are well known and described in numerous books and publications. Results from the use of an .amine salt of a. long-chainfaliphatic alcohol sulfate, sold by .E. I. du Pont de Nemours & C0,, known by the trademark Duponol -:OS,;a clear. amber, oily, water-insoluble liquid, are typical! f Application .Serial'No.'383,908, filedzOctober 2, 1953, describes the' small, hollow, gas filled; hole-free particles and methods of making the same, 'and this disclosure to the extent deemed necessaryis incorporated by reference. To understand the present invention it is believed-necessary here to say only that the particles'maybe made from any film-forming material, .natural or synthetic. The preferred method is to spray dry a solution of the material containing a blowingagent. Most of the ma.- terials, especially those formedfrom a water solution, while wettable to some extent either by non-aqueous liquids'. or water, are preferentiallywettable by water. The present invention. is intended to cover all such filmforrning materials and especiallyforthose.filrn-forming materials from whose surfaces water'will .displace..the substrate liquid. v

The non-aqueous ;volatilelliquids to be protected include hydrocarbons, such as gasoline, kerosene, and crude oil,. halogenated derivatives of hydrocarbons such as carbon tetrachloride or .perfluoroheptane, and esters and ethers such as ethyl acetate and diethylether. These liquids seldom contain more than traces or minor amounts of water and are notmiscible with any substantial por-' tion of water. Thje'presence, of such minor. amountsof water does not appreciably affect the rates .of evaporation of these liquids when coveredwith a floating layer of hollow particlestreated' in accordance with thepresent invention. p 2' There are several methods fortreatingthefsmallpagticles with the surface-active agent. i First, the surfaceactive agent may be incorporated in the composition which is spray dried to produce these particles. Second, the surface-active agent and particles maybe mixed to gether by any conventional meanspsuch as by. spraying the surface-active agent or a solution-thereof on the particles or by immersing the particles in the surfaceeactive agent or a solution thereof. Third, the'agent might be added to a foam in the form of a slurry of these particles in a non-aqueous liquid, such as the volatile nonaqueous liquid to be covered. Fourth, the surface-active agent may be added directly to the volatile non-aqueous Table II Percent by Volume of Original Product Lost When Covered Evapora- Bytion Loss Product Covered Reduction p in Percent None Untreated Treated Particles Particles Gasoline; 46 46 23 50 Tractor Fuel 1 36 29 10. 5 B4 Stra'ght Run Naphtha 54 60 25 60 liquid to be covered and will be absorbed on the surface of the particles.

By treatment with a surface-active agent, the wetting preference of these particles for water is reduced as compared to their preference for the liquid to be protected. Tests indicate that evaporation loss reduction occasioned by the use of these treated particles is substantially greater than with untreated particles.

The invention will be illustrated by the following examples. Except where otherwise mentioned, the small, hollow, hole-free, gas filled particles used were produced from a phenol-formaldehyde resinous composition by spray drying, as described heretofore.

EXAMPLES 1,-7

Mixtures of water-insoluble surface-active agents and technical grade toluene were covered to a depth of 0.5 inch with particles previously exposed to a humid atmosphere, and the wetting efiect was noted. Results are shown in Table I.

1 This example illustrates why operable surface-active agentsin the present invention exclude nonionic agents. i I 1 B-bydroxyethyl 2-heptadecenyi glyoxalidine. sold by Union Carbide and Carbon Corporation.

Amine salt of a long-chain aliphatic alcohol sulfate; sold by E. I. du Pont; de Nemours & Co.

These examples show that the water-insoluble, ionic, surface-active agents do improve the ability of the par ticles to be wetted preferentially by toluene. Examples 1 and 7 were allowed to stand overnight. An appreciably greater volume of toluene was lost by evaporation from Example 1, thereby indicating the ability of a wetted layer of particles to reduce the rate of evaporation. This ability was further tested in Example 8.

EXAMPLE 8 The unexpected ability of a floating layer of treated particles to reduce evaporation losses as compared with a layer of untreated particles and also with no layer was tested by measuring the respective volumes lost after storage for a period of one week of a regular grade gasoline, a straight run naphtha, and a tractor fuel. The layer was produced by making a slurry of a batch of particles suflicient to provide a one-inch thick layer with the product to be covered. Duponol OS in an amount equal to 2%, based onthe weight of particles, was added to the slurry when treated particles were required. Reiults'are'shownin Table II."

1 Blend of equal volumes of gasoline and kerosene. V

These tests show that untreated particles have a slight inhibiting action on evaporation and that treated particles will reduce evaporation by as much as 50% or more.

EXAMPLES 9-14 -To determine the effect on rate of evaporationof a ing composition were prepared by making a slurry of gasoline, particles, and Duponol OS, and adding the slurry to gasoline:

. t Parts by Weight of Components 1 1 Example Nos.

1 e Gasoline Particles Duopgnol Total 646 none none 646 577 23 none 600 612 23 l 0. 05 635 581 23 1 605 567 23 9 599 500 46 .18 564 1 Enough for monomolecular coating of all particles.

The thickness of the particle layer was one inch in samples 10-13 and two inches in sample 14. These samples were allowed to stand and the cumulative loss of gasoline was noted.

Table III Cumulative Volume Lost by Evaporation Percent of Original Volume Cumulative Time in Hours Example No.

data :not only show that a layer of particles will 'reduee evaporation rates, but, surprisingly, that their 'effectiyenessi'in this respect. is markedly improved 'by fthe concurrent use of small amounts of a surface active agent. The use of such an'agent in Sample ll, namely an amount equal to 0.22% by weight of the particles, was "sufficient to reduce the rate or evaporation to the extent thafl'a'bout 42-l1our's were requiredbefore the volume lost (33%) was about equal to that lost (32%) in 24 hours Ywhen using: untreated particles. Where the amount of'agent was 39%, evaporation rates were re-. duced by a factor of about 9, that is, it required 18 hours for 8.1% evaporationin Example' 13, as compared with only 2' hours for the same evaporation (8%) in Example 9: 3

to be lost through evaporation. Table IV shows the hours required for the evaporation of 10, 20, and 30% by volume of the gasoline in each of Examples 9-14, inclusive, the values being obtained from a graph of the data in Table III.

Table IV Hours for Evaporation of- Example N0.

1 designates extrapolated values.

EXAMPLES -17 In these examples a solution comprising 90% by volume of kerosene and 10% of a solvent-extracted bright stock was prepared, and 400 ml. thereof was placed in each of three different 1000 ml. beakers. The surface of each sample was covered with particles to a depth of about 0.5 inch. The surface active agent was added to each of two beakers in the form of a 5% solution in kerosene whereby the total amount of agent was equal to approximately 2% by weight of the particles. After standing overnight, the three beakers were treated as follows:

Each day twelve successive applications of 5 m1. of water were made dropwise on each sample over a period of approximately four hours, and the condition of the floating layers noted. This method was followed daily until each floating layer had broken, thereby leaving the surface of the underlying hydrocarbon exposed. The total amount of water added in order to break the layer Was used as a criterion of the effectiveness of the wetting agents. The results are set forth below in Table V.

Table V ml. of Water Required to Break Layer of Particles Example No. Surface-Active Agent N nne Duponol OS Lecithin Both wetting agents showed improvement over the blank, lecithin being the most effective.

While the invention has been described with reference to specific embodiments, it will be apparent to those non-aqueous liquid products which comprises covering the surface of said products with a floating layer of individual and separate, small, hollow, gas-filled, hole-free particles of a solid material inert to said volatile product and preferentially wet by water, which particles have an average diameter of less than 500 microns and a liquid displacement density of from 0.05 to 0.6, the improvement which comprises contacting said particles with a water-insoluble, ionic, surface-active agent in an amount less than 40% by weight of said particles to render said particles less sensitive to water.

2. The method of claim 1 in which the particles are formed from a resin obtained by condensing formaldehyde with a compound selected from the group consisting of phenol and urea.

3. The method of claim 1 in which said agent is an aliphatic water-insoluble alcohol sulfate. 0

4. In a method of preparing a material adapted to be applied to a volatile liquid to inhibit the evaporation thereof, the step of contacting individual and separate, small, hollow, gas-filled, hole-free particles of a solid material inert to said liquid and preferentially wet by water, which particles have an average diameter of less than 500 microns and a liquid displacement density of from 0.05 to 0.6, with an amount less than 40% by weight of said particles of a water-insoluble, ionic, surface-active agent to render said particles less sensitive to water.

5. The method of claim 4 in which the particles are contacted with the surface-active agent dissolved in a water-immiscible solvent.

6. The method of claim 5 in which the solvent is the volatile liquid to be protected.

7. The method of claim 4 in which the particles are formed from a resin obtained by condensing formaldehyde with a compound selected from the group consisting of phenol and urea.

8. A material adapted to inhibit the evaporation of a volatile liquid, comprising individual and separate, small, hollow, gas-filled, hole-free particles of a solid material inert to said liquid and preferentially wet by water, which particles have an average diameter of less than 500 microns and a liquid displacement density of from 0.05 to 0.6, having on their surface an amount less than 40% by weight of a water-insoluble, ionic, surface-active agent to render said particles less sensitive to water.

9. The material of claim 8 in which the particles are formed from the condensate of formaldehyde with a compound selected from the group consisting of phenol and urea.

References Cited in the file of this patent UNITED STATES PATENTS 1,415,351 Howard May 9, 1922 1,415,352 Howard May 9, 1922 1,479,790 Davis Jan. 8, 1924 1,985,491 Fisher Dec. 25, 1934 2,101,635 Bender Dec. 7, 1937 2,170,644 Nelson Aug. 22, 1939 FOREIGN PATENTS 200,855 Great Britain July 26, 1923 OTHER REFERENCES De Ment: Abstract of application S. N. 301, pub. June 30, 1953, 671 0. G. 1497.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,822,238 February 4, I958 Richard D, Croft et alt.

It ishereby certified that" error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the headingto the printed specification, lines 2 and 3, title of. invention; SURFACTANT TREATMENT OF MICROBALLOONS 'TO IMPROVE WATER RESISTANCE" read SUBFACTANT TREATMENT OF SMALL HOLLOW, HOLE-FREE PARTICLES TO IMPROVE WATER RESISTANCE.

Signed and sealed this 3rd day of June .1958,

(SEAL) Attest:

KARL MINE ROBERT c. WATSON Attesting Officer I Conmisaioner of Patent; 

1. IN THE METHOD OF INHIBITING EVAPORATION OF VOLATILE NON-AQUEOUS LIQUID PRODUCTS WHICH COMPRISES COVERING THE SURFACE OF SAID PRODUCTS WITH A FLOATING LAYER OF INDIVIDUAL AND SEPARATE, SMALL, HOLLOW, GAS-FILLED, HOLE-FREE PARTICLES OF A SOLID MATERIAL INERT TO SAID VOLATILE PRODUCT AND PREFERENTIALLY WET BY WATER, WHICH PARTICLES HAVE AN AVERAGE DIAMETER OF LESS THAN 500 MICRONS AND A LIQUID DISPLACEMENT DENSITY OF FROM 0.05 TO 0.6, THE IMPROVEMENT WHICH COMPRISES CONTACTING SAID PARTICLES WITH A WATER-INSOLUBLE, IONIC, SURFACE-ACTIVE AGENT IN AN AMOUNT LESS THAN 40% BY WEIGHT OF SAID PARTICLES TO RENDER SAID PARTICLESS LESS SENSITIVE TO WATER. 